Re: [PATCH] arm64: restore bogomips information in /proc/cpuinfo

[Shi, Yang]

On 11/25/2015 7:16 AM, Nicolas Pitre wrote:
> On Wed, 25 Nov 2015, Jon Masters wrote:
>
> > On 11/18/15, 1:15 PM, Yang Shi wrote:
> >
> > > As what Pavel Machek reported [1], some userspace applications depend on
> > > bogomips showed by /proc/cpuinfo.
> > >
> > > Although there is much less legacy impact on aarch64 than arm, but it does
> > > break libvirt.
> > >
> > > Basically, this patch reverts commit
> > > 326b16db9f69fd0d279be873c6c00f88c0a4aad5
> > > ("arm64: delay: don't bother reporting bogomips in /proc/cpuinfo"), but with
> > > some tweak due to context change.
> >
> > On a total tangent, it would be ideal to (eventually) have something reported
> > in /proc/cpuinfo or dmesg during boot that does "accurately" map back to the
> > underlying core frequency (as opposed to the generic timer frequency). I have
> > seen almost countless silly situations in the industry (external to my own
> > organization) in which someone has taken a $VENDOR_X reference system that
> > they're not supposed to run benchmarks on, and they've done it anyway. But
> > usually on some silicon that's clocked multiples under what production would
> > be. Then silly rumors about performance get around because nobody can do
> > simple arithmetic and notice that they ought to have at least divided by some
> > factor.
>
> Be my guest my friend.
>
> According to the common wisdom, the bogomips reporting is completely
> senseless at this point and no one should expect anything useful from
> it. Therefore I attempted to rehabilitate some meaning into it given
> that we just can't get rid of it either and it continues to cause
> dammage. You certainly saw where that has led me.

Or we may create a new one, i.e. "cpu MHz" like x86? Then we keep both 
in cpuinfo so that the userspace could adopt it gradually?

Thanks,
Yang

> Nicolas

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